Re: [PATCH v2 06/17] x86/ldt: Do not install LDT for kernel threads

[Andy Lutomirski]

On Thu, Dec 14, 2017 at 11:43 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Thu, Dec 14, 2017 at 12:27:32PM +0100, Peter Zijlstra wrote:
>> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>>
>> Kernel threads can use the mm of a user process temporarily via use_mm(),
>> but there is no point in installing the LDT which is associated to that mm
>> for the kernel thread.
>
> So thinking about this a bit more; I fear its not correct.
>
> Suppose a kthread does use_mm() and we then schedule to a task of that
> process, we'll not pass through switch_mm() and we'll not install the
> LDT and bad things happen.
>
> Or am I missing something?
>

Nah, you're probably right.